Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SHUTTLE/SHUTTOUT.TXT

Text File | 1993-02-05 | 22KB | 359 lines

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THE VERSATILE SPACE SHUTTLE:  WORKHORSE OF THE NEW FRONTIER

     The Space Shuttle is the first reusable aerospace vehicle.  It takes off
vertically like a rocket.  The winged orbiter then maneuvers in orbit like a
spaceship.  At the end of the mission the orbiter lands on a runway like an
unpowered glider.  The delta-winged orbiter is about the size and general shape
of a DC-9 jetliner.
     The Shuttle orbiter can be used as an observation platfform, from which
instruments can be focussed on the ground passing below, or objects in space of
strong interest to astronomers.  The orbiter can also carry a small but fully
equipped manned laboratory, called Spacelab, for medical, scientific,
engineering, and industrial experiments.  Spacelabs have been flown on four
successful missions. The pressurized modules remain in the cargo bay of the
orbiter throughout the mission.
     One of the key attributes of the Space Shuttle is the relatively low
acceleration and deceleration forces exerted on crew and passengers during
launch and reentry.  These forces reach a peak of 3 G's -- three times the
force of gravity on the Earth's surface -- for a few minutes at a time.  The
strain is well within the limits which can be tolerated by healthy people.


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                THE ORBITER CREW COMPARTMENT
     The living space aboard an orbiter is relatively roomy and comfortable,
compared to that in earlier manned spacecraft.  There are two floors in the
pressurized crew cabin located in the nose section.  Together they provide 71.5
cubic meters (2,525 cubic feet) of space.  The temperature can be regulated to
stay between 16 and 32 degrees Celsius (61 and 90 degrees Fahrenheit).
     The top level of the cabin is the flight deck.  Here the commander and
pilot monitor and operate a sophisticated array of controls that are far more
complicated than those of a giant jetliner.  Behind their seats is a work area
for mission and payload specialists.  These crewmembers operate experiment
controls, and check out and deploy spacecraft carried inside the large,
unpressurized cargo bay. The bottom level of the cabin is the mid deck.  This
is the living quarters for the crew, although experiments that require air,
such as plants and small animals, can also be carried here.  The mid deck
contains lockers for stowing crew equipment, and facilities for sleeping,
eating, personal hygiene, and waste disposal.
     Air pressure inside the crew compartment is the same as Earth's at sea
level: 1,033 grams per square centimeter (14.7 pounds per square inch).  This
atmosphere is made up of 80 percent nitrogen and 20 percent oxygen.  Earth's
atmosphere is 78 percent nitrogen, 21 percent oxygen, and one percent other
gases, such as argon and neon. The crew members wear ordinary clothing.  They
don the bulky spacesuits only for extravehicular activities outside the cabin.
     Fans circulate the cabin air through cleansing filters, which are changed
regularly.  These filters contain activated charcoal to remove odor, and
lithium hydroxide to remove carbon dioxide.  Excess moisture is also removed,
keeping the humidity at comfortable levels. The air in an orbiter is cleaner
than that on Earth.  Hay fever sufferers would welcome such a pollen-free
atmosphere.


                WHAT SPACE TRAVELERS EAT
     The one, two, and three-person crews in earlier programs ate their meals
out of containers or pouches, most commonly prepared by adding water and
kneading the mixture by hand.  The food was nutritious, but not very
appetizing.  The Space Shuttle carried eight people on one mission, and seven
has been a common number.  For these large crews, or missions planned to last
for a week or more, a galley "mission kit" can be loaded in the orbiter mid
deck.
     The mid deck galley includes special serving trays that hold the different
food containers in place in microgravity.  It also has a convection-type oven
where packages of food are warmed before going into the trays.  A small dining
area, consisting of a table and several foot loops, is  optional on each
mission.  The foot loops are floor restraints that help the astronauts steady
themselves and remain in place while eating.
     If no galley is loaded aboard, the astronauts eat virtually the same
meals, but they are heated inside a food warmer the size of a suitcase.
Earth-bound chefs might envy meal preparation on the orbiter.  One crew member
can prepare meals for four people in about five minutes (excluding heating
time).
     The orbiter does not normally carry a refrigerator because of the weight.
If one is needed for biomedical experiments, and extra room is available, foods
such as ice cream and frozen steaks may be added to the astronaut menu.
     About half the Shuttle foods and beverages are preserved by dehydration,
which saves both weight and storage space.  There is ample water for
rehydration, since the fuel cells that power the orbiter produce it as a
by-product when generating electricity. (Both hot and cool water are
available.)  Some foods are thermo- stabilized -- that is, heat-sterilized and
then sealed in conventional cans or plastic pouches.  A few, such as cookies
and nuts, are available in a ready-to-eat form.
     Meals in orbit are both tasty and nutritious.  The menu includes more than
70 food items and 20 beverages.  With so many different choices available,
astronaut crews can have a varied menu every day for four days.
     What are these meals in space like?  The menu for a typical day might
start with orange drink, peaches, scrambled eggs, sausage, cocoa and a sweet
roll for breakfast; cream of mushroom soup, ham and cheese sandwich, stewed
tomatoes, banana and cookies for launch; and shrimp cocktail, beefsteak,
broccoli au gratin, strawberries, pudding and cocoa for dinner.
     The carefully selected menus provide about 3,000 calories per person
daily, although crew members are not required to eat that much.  Previous space
missions demonstrated that astronauts need at least as many calories in space
as they do on Earth.
     Meals served on the Space Station, at least at the beginning, will
resemble those available on the Space Shuttle.  Later, perhaps small vegetable
gardens will supply fresh produce, as well as absorb carbon dioxide from the
atmosphere while supplying oxygen for the crew.


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                        SANITATION IN ORBIT
     Sanitation is more important within the confines of a spaceship or space
station than on Earth.  Studies have shown that the population of some microbes
can increase extraordinarily in microgravity and confined spaces.  This means
many infectious illnesses could easily spread to everyone aboard.
     The eating equipment, dining area, toilet, and sleeping facilities in an
orbiter are regularly cleaned, to prevent the growth of microorganisms.  Since
there is no washing machine aboard, trousers (changed weekly), socks, shirts,
and underwear (changed every two days) are sealed in air tight plastic bags
after being worn.  Garbage and trash are also sealed in plastic bags.
     Shuttle travelers don't have to do many dishes.  Food containers go into
the plastic bags, and eating utensils and trays are cleaned with wet wipes.
     A favorite early question of people interested in space was how the
astronauts took care of digestive elimination.  The orbiter travelers use a
toilet that operates very much like one on Earth.  A steady flow of air moves
through the unit when it is in use, carrying wastes to a special container or
into plastic bags.  The container can be opened to vacuum, which exhausts the
water and dries the solids, and the plastic bags, when used, can be sealed.
     Some of the wastes may be returned to Earth for postflight laboratory
analysis.  In the past, such analyses have helped doctors understand how the
body functions in microgravity, including data on which minerals the body loses
in unusual amounts.
     Unlike Skylab, which had an enclosed shower, Shuttle travelers can only
take sponge baths in space.  Water droplets float about in weightlessness,
creating a potential hazard for electrical equipment. Water is obtained from a
handgun, where the temperature can be set at any comfortable level from 18 to
35 degrees C (65 to 95 degrees F). Dirty water from the sponge is squeezed into
an airflow system which conveys it to the orbiter's waste collection tank.
     Whiskers cut off in shaving could also become a nuisance if they floated
about, with a potential to damage equipment.  Male astronauts can avoid this
problem by using conventional shaving cream and a safety razor, then cleaning
off the face with a disposable towel.
     The sleeping and sanitary arrangements for the Space Station are still in
the design stage.  Engineers are drawing on the experience gained in earlier
manned space flight programs to plan systems that will be more like those on
Earth.  Eventually, a visitor to the Space Station should be able to eat a meal
or use the sanitary facilities without special instructions.


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                SPACESUITS AND RESCUE EQUIPMENT
     In earlier programs spacesuits were tailor-made for each astronaut, a
time-consuming and expensive process.  Now only the gloves are custom-fitted.
The  Shuttle spacesuit is made in small, medium, and large sizes, and can be
worn by either men or women.  The suit comes with an upper and lower torso,
equivalent to a shirt and trousers, and the two pieces snap together with seal
rings.  A life- support system comes built into the upper torso.  All earlier
versions had separate support systems that had to be connected to the suits.
     The Shuttle spacesuit is lighter, more durable, and easier to move about
in than its predecessors.  It is only used for an extravehicular activity (EVA)
outside the crew cabin.  The astronauts wore pressure suits, of the kind worn
by military jet pilots, during early test flights.  Now they wear regular
clothing.
     Only two spacesuits are normally carried on a flight.  If a transfer from
one vehicle to another should be necessary in the future, personal rescue
enclosures are available for the remaining crew members.  These are 83.36
centimeter (34-inch) diameter (when pressurized) spheres, each containing life
support and communications gear.
     In an emergency in space that required  abandoning the orbiter, two
astronauts would don the spacesuits and, if needed, the Manned Maneuvering
Units (MMUs).  The latter have built-in propulsion systems.  The rest would
enter the personal rescue enclosures.  The two suited astronauts would transfer
their crewmates to the rescue ship.  This could be accomplished by rigging a
pulley and clothesline device between the two vessels, using the Canadarm
Remote Manipulator System, or physically towing the enclosures through space
with the power of the MMUs.

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                RECREATION AMD SLEEPING
     Just as on Earth, recreation and sleep are important to good health when
working in space.  Astronauts perform a scientifically planned exercise
program, largely to counter the atrophy some muscles experience in a weightless
environment.  Cards and other games, books, and taped music can be taken
aboard.  Tape recorders are available.
     Sleeping accommodations aboard the Shuttle vary, depending on the
requirements of the particular mission.  On the first flight, astronauts Young
and Crippen slept in the commander and pilot seats. They wanted to be instantly
available if needed.  Later crews slept in their seats, in sleeping bags, in
bunks, or by simply tethering themselves to the orbiter walls.
     The sleeping bags are cocoon-like restraints attached to the lockers where
crew provisions are stored.  In microgravity there is no 'up,' and the
astronauts can sleep as comfortably in the vertical position as the horizontal.
     A bunkbed kit was available by the time of the STS-9 mission. Crew members
could sleep in three horizontal bunks when these were installed, and an extra
vertical bunk was available if needed.  Each bunk comes complete with an
individual light, communications station, fan, sound suppression blanket, and
sheets with microgravity restraints.  The bunks even have pillows.
     When the bunks must be removed to allow room in the mid deck for
experiments or extra equipment, up to four optional sleeping bags can be used
instead.


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            THE CONTINUING CHALLENGE OF MICROGRAVITY
     Many of the problems that arise from living and working in space have been
resolved.  However, some of the physiological affects of weightlessness are
still not completely understood.  Among these are the leaching of certain
minerals from bones; atrophy of muscles when not exercised; and space
adaptation syndrome, a form of motion sickness found only in spaceflight.
     All the deleterious effects of living in microgravity disappear after an
astronaut returns to the ground.  Some can be countered while in orbit by
special diet and exercise.  But even a vigorous exercise program does not
appear to stop bone loss, or the decrease in the rate of normal bone
formation.  NASA is engaged in a long-term program to understand the causes
underlying these changes, in order to develop ways to prevent them.  This will
be particularly important for the longer tours of duty on the Space Station,
where crew members will be in orbit for three months or more at a time.
     The Space Station NASA is now planning and designing is a large facility.
It will be resupplyable and capable of staying in orbit indefinitely, unlike
Skylab.  Many of its systems will be highly automated, leaving the crew more
time for the tasks that can only be performed by humans.  Present plans call
for the initial configuration to be in operation by the middle of the 1990's.
     The Space Station will be a permanent, multi-purpose facility operating in
orbit.  It will serve as a laboratory, to conduct long- term basic research in
the almost perfect vacuum and microgravity of space; a manufacturing plant, to
make exotic metal alloys, super-pure pharmaceuticals, or perfect crystals; a
spacecraft garage and repair facility; and a base for the assembly in orbit of
other large structures.  It will also support nearby free-flying Earth
observation, astronomy, and materials processing platforms, among many other
applications.  There will a tremendous amount and variety of work to do.
     Initial plans call for a crew of six to eight people in the operational
Space Station, supported by resupply and crew rotation flights of the Space
Shuttle every three months.  One major advance planned for the Space Station is
a closed-cycle environmental control and life support system.  The oxygen will
be recovered from the carbon dioxide exhaled by the crew, and the wash water,
urine, and condensate will be purified and reused.  Present planning calls for
only food and nitrogen to be periodically resupplied from Earth.
     The Space Station Revised Baseline Configuration features a 110-meter long
horizontal boom to which pressuried modules are  attached  in the Center.  One
of the modules is a habitat, and the other three are laboratories provided by
the U.S., the European Space Agency, and Japan.  The standard module will be
13.3 meters (43.7 feet) long and approximately 4.5 meters (15 feet) in
diameter.  They will be connected by tunnels and various support structures.
The Space Station will provide far more working and living room than any
earlier facility designed to operate in space.
     Several other nations and space organizations are working cooperatively
with NASA to design and build some components of the Space Station.  They too
will have personnel living and working aboard.  The Space Station has been
called "the next logical step" in the continuing exploration and utilization of
space, the new frontier mankind has only started to explore. Improving the
living and working conditions of the people involved is an important part of
the total effort.


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FLASHBACK FOR THE SPACE BACKPACK


Reprinted from the February 3, 1989, issue of
Space News Roundup,
a publication of NASA's Lyndon B. Johnson Space Center,
Houston, Texas

Manned maneuvering unit celebrates fifth anniversary

     On Tuesday, it will be exactly five years since astronaut
Bruce McCandless pushed a lever and became the first space walker
to fly freely above Earth.
     McCandless' untethered flight with the manned maneuvering
unit (MMU) was the fruition of a dream that had been moving
toward reality since the early 1960s, a dream enjoyed by many at
JSC. This center managed and performed much of the work on the
MMU, which was built by Martin Marietta.
     On Feb. 7, 1984, McCandless piloted the nitrogen-jet
propelled MMU a little more than 100 yards from Challenger,
creating a scene of space-age freedom that became immediately
famous as it fired the public imagination. McCandless was
accompanied by astronaut Bob Stewart who flew a second MMU.
Together, the two tested the units and found their performances
flawless.
     It was a triumphant moment for both McCandless and Ed
Whitsett, project engineer for the MMU and a man involved with
the concept since his graduate thesis in 1960. The two had worked
together on the MMU off and on for about 16 years.
     "We had a lot of confidence in it. We knew it was a good
machine," Whitsett said recently. "But, obviously, the first time
he flew away from the Shuttle, a lot of people were uptight."
     That was not the case for McCandless. "I had lot of
confidence in the hardware," he said. "I knew that the laws of
physics hadn't been repealed recently."
     McCandless said he experienced no new physical sensations as
he became, essentially, a second spacecraft. After having been in
orbit aboard Challenger for four days, the only difference he
felt in the MMU was "a sense of professional satisfaction."
     "I did not feel alone or isolated," he remembered. "I
attribute that largely to excellent radio communications. Vance
(Brand) and the guys were reading off ranges and talking to me,
so I didn't feel I was isolated."
     The first flight was the result of development work that
began with an awkward, difficult-to-control, hand-held
maneuvering unit used during the Gemini program. The work
proceeded through the Skylab missions, where crew members
evaluated another hand-held unit, a device called "jet shoes" and
the first backpack thruster unit. Among these three, the
backpack, flown by five different astronauts for a total of 14
hours within the orbital workshop, easily won.
     Development of the MMU during the Shuttle program was
spurred, at first, by a desire to have a method the crew could
use to inspect the bottom of the Orbiter in flight, Whitsett
said. But its major use, and the event that put its operation in
high gear, was a need for satellite retrieval and repair.
McCandless' flight was a dress rehearsal for repairs of the Solar
Maximum Mission satellite.
     The MMU was used on two following Shuttle flights to work
with three satellites_Solar Max, Westar VI and Palapa B-2. All of
the flights took place within a year, and, in total, six
astronauts have flown MMUs for a combined 10 and a half faultless
hours.
     MMUs aren't currently scheduled for any future flights,
although it is possible they will be used for a Space Station
Radiator Assembly Demonstration (SRAD) flight experiment sometime
in 1993. Still, Whitsett said, one can never tell when the need
could arise for an MMU mission.
     "The Westar and Palapa mission wasn't planned far in
advance. It just happened that the MMU was needed," he explained.
     The MMUs, proven dependable fliers, are in storage now at
Martin Marietta. "They're in good shape, able to be used whenever
the need arises again," McCandless said.
     Completing development of the MMU, a project that spanned so
many years, was a little bittersweet for those devoted to it.
"Everybody who worked on it was extremely enthusiastic. People
were nearly fighting to get on the project," Whitsett said. "It's
sort of like raising a child. When they go off and get married,
you're still proud of them. But they're not there anymore."
     Many of those involved with development and flight of the
MMU plan to honor the fifth anniversary of the first flight on
Tuesday.
     The MMUs remain ready and waiting as they are, but they may
be improved by work now under way on the Extravehicular Activity
(EVA) Retriever, a fetching space robot being developed at JSC.
"A lot of the retriever work will feed into MMU updates, such as
a fault detection system and caution and warning lights," said
Whitsett, who now works as systems integration manager for space
station EVA systems.
     McCandless also has special ideas for the future of the MMU.
"I'd dearly love to see us mount the IMAX camera on the MMU for a
flight," he said. "You could get stand-off imagery of the Orbiter
with Earth in the background. I think that would be very
dramatic."
     McCandless said he does have one minor regret about the
first MMU flight. "I had intended when I got out 30 feet or so to
stop and face away from Orbiter and look at the cosmos," he said.
"I forgot; I was concentrating on watching the Orbiter."
     McCandless is now deeply involved in preparing for another
Shuttle flight, STS-31. Scheduled for December, the mission's
primary objective will be to deploy Hubble Space Telescope.

     -END-